FIG. 22 is a view showing the schematic configuration of a part relating to the charging system of a plug-in hybrid vehicle disclosed in Patent Document 1. In the charging system shown in FIG. 22, in a vehicle whose electric storage device is charged with power from an external power source, a pilot signal CPLT from a control pilot circuit 334 inside a charging cable 300 is used as an activating signal for the charging system.
FIG. 23 is a view illustrating the charging system shown in FIG. 22 in more detail. In addition, FIG. 24 is an example of a timing chart of the pilot signal CPLT shown in FIGS. 22 and 23. As shown in FIG. 23, the control pilot circuit 334 inside the charging cable 300 has a voltage sensor 604 and an oscillator 602. The oscillator 602 is operated by the power supplied from a power source 402.
As shown in FIG. 24, the oscillator 602 outputs a non-oscillation signal when the voltage of the pilot signal CPLT detected by the voltage sensor 604 is close to a specified initial voltage V(1) (e.g., 12 V), and outputs a signal oscillating at a specified frequency (e.g., 1 kHz) and at a specified duty cycle when the voltage lowers to a specified oscillation voltage V(2) (e.g., 9 V) that is lower than V(1). Furthermore, the control pilot circuit 334 supplies a current to an electromagnetic coil 606 when the voltage of the pilot signal CPLT is close to a specified voltage V(3) (e.g., 6 V). When the current is supplied from the control pilot circuit 334, the electromagnetic coil 606 generates an electromagnetic force and turns on a relay 332.
The voltage of the pilot signal CPLT is adjusted by switching the resistance value of the resistance circuit 502 of an ECU 170. The ECU 170 includes the resistance circuit 502, input buffers 508 and 510, and a CPU (Control Processing Unit) 520. The resistance circuit 502 includes pull-down resistive elements R(2) and R(3) and switches SW(1) and SW(2). The CPU 520 includes a CPU 512 and a CPU 514.
The pull-down resistive element R(2) and the switch SW(1) are connected in series between a control pilot line L(1) to which the pilot signal CPLT is transmitted and a vehicle earth 518. The pull-down resistive element R(3) and the switch SW(2) are connected in series between the control pilot line L(1) and the vehicle earth 518 and further connected in parallel with the series-connected pull-down resistive element R(2) and switch SW(1).
The switch SW(1) is turned on/off by a control signal from the CPU 512. When the switch SW(1) is turned on, the pull-down resistive element R(2) and the vehicle earth 518 become a connection state. When the switch SW(1) is turned on, the pull-down resistive element R(2) and the vehicle earth 518 become a non-connection state. In a state in which charging is not performed, the switch SW(1) is off, and the pull-down resistive element R(2) and the vehicle earth 518 are in the non-connection state. In other words, when the charging cable 300 is connected to the vehicle, the switch SW(1) is off, and the pull-down resistive element R(2) and the vehicle earth 518 are in the non-connection state.
A power source 516 whose supply power is controlled by a control signal from the CPU 514 is connected to the switch SW(2). When power is supplied from the power source 516 to the switch SW(2) by the control signal from the CPU 514, the switch SW(2) is turned on, and the pull-down resistive element R(3) and the vehicle earth 518 become a connection state. When the power from the power source 516 to the switch SW(2) is shut off by a control signal from the CPU 514, the switch SW(2) is turned off, and the pull-down resistive element R(3) and the vehicle earth 518 become a non-connection state. In a state in which charging is not performed, the switch SW(2) is off, and the pull-down resistive element R(3) and the vehicle earth 518 are in the non-connection state.
The resistance circuit 502 switches the voltage of the pilot signal CPLT when the switches SW(1) and SW(2) are turned on/off depending on the control signals from the CPU 520. In other words, when the switch SW(1) is turned off and the switch SW(2) is turned off depending on the control signals from the CPU 520, the pull-down resistive elements R(2) and R(3) respectively become a state of being unconnected to the vehicle earth 518, and the voltage of the pilot signal CPLT is maintained at the initial voltage V(1). Hence, the pilot signal CPLT is maintained in a non-oscillation state.
In a state in which the switch SW(1) is off, when the switch SW(2) is turned on depending on the control signal from the CPU 520, the pull-down resistive element R(3) is connected to the vehicle earth 518, whereby the voltage of the pilot signal CPLT lowers to the oscillation voltage V(2). Furthermore, when the switch SW(1) is turned on depending on the control signal from the CPU 520, the pull-down resistive elements R(2) and R(3) are respectively connected to the vehicle earth 518, whereby the voltage of the pilot signal CPLT further lowers to the specified voltage V(3).
FIG. 25 is a flow chart showing the operation of the CPU 520 in the charging system disclosed in Patent Document 1. At step S100, the CPU 520 judges whether the voltage VL(1) of the pilot signal CPLT has changed from a voltage V(0) to the initial voltage V(1). When the voltage has changed to the initial voltage V(1) (YES at step S100), the CPU 520 starts up the charging system at step S102. For example, in the case that the CPU 512 has performed the process of the above-mentioned step S100, the CPU 512 transmits a command for activating the CPU 514 to the CPU 514.
Next, at step S104, the CPU 520 judges whether the start-up of the charging system is completed. For example, in the case that the CPU 512 has received a response signal corresponding to the activating command of the above-mentioned step S102, the CPU 520 judges that the start-up of the charging system is completed. Next, at step S106, the CPU 520 transmits the control signal for turning on the switch SW(2) to the switch SW(2). Next, at step S108, the CPU 520 starts preparation for charging. For example, the CPU 520 judges whether charging from the charging cable 300 is possible on the basis of the SOC (State Of Charge) of the electric storage device, the rated current detected depending on the duty of the pilot signal CPLT, etc.; in the case that the CPU 520 judges that charging is possible, converters and inverters provided along the route from the external power source to the electric storage device are caused to stand by in an operable state.
Next, at step S110, the CPU 520 judges whether the preparation for charging is completed. When it is judged that the preparation for charging is completed (YES at step S110), the CPU 520 transmits the control signal for turning on the switch SW(1) to the switch SW(1) at step S112). Next, at step S114, the CPU 520 turns on a relay switch on the route of charging and starts charging. At step S116, the CPU 520 judges whether charging is completed. When it is judged that charging is completed (YES at step S116), the CPU 520 transmits the control signals for turning off the switches SW(1) and SW(2) to the respective switches at step S118.
The change of the pilot signal CPLT on the basis of the operation of the CPU 520 described above will be described referring to FIG. 24. When the user connects the charging cable 300 to the power outlet 400 of the external power source at time T(1), the power from the power source 402 is supplied to the control pilot circuit 334, and the voltage of the pilot signal CPLT rises from the voltage V(0) (0 V) to the initial voltage V(1) as shown in FIG. 24. When the user connects the charging cable 300 to the charging inlet 270 of the vehicle at time T(2), the pilot signal CPLT is input to the control pilot line L(1) on the side of the vehicle.
If a configuration is used in which the resistance circuit 502 provided for the ECU 170 of the charging system is not provided with the switch SW(2), the pull-down resistive element R(3) is in a state of being connected to the vehicle earth 518 at all times; hence, at time T(2) when the charging cable 300 is connected to the vehicle, the voltage of the pilot signal CPLT lowers from the initial voltage V(1) to the oscillation voltage V(2), and the oscillator 602 of the charging cable 300 causes the pilot signal CPLT to oscillate (refer to the alternate long and short dash line B of FIG. 24). However, in the charging system according to Patent Document 1, the switch SW(2) is provided between the pull-down resistive element R(3) and the vehicle earth 518; in a state in which charging is not performed although the charging cable 300 is connected to the vehicle, the switch SW(2) is turned off, whereby the pull-down resistive element R(3) and the vehicle earth 518 are set to the non-connection state.
As a result, as indicated by the solid line A of FIG. 24, the voltage of the pilot signal CPLT is maintained at the initial voltage V(1) even when the charging cable 300 is connected to the vehicle at time T(2). Hence, in the case that the voltage VL(1) has changed from V(0) to V(1), the CPU 520 judges that the charging cable 300 has been connected to the vehicle, whereby the start-up of the charging system is started.
Moreover, when the start-up of the charging system is completed and the switch SW(2) is turned on at time T(3), the voltage of the pilot signal CPLT lowers to the oscillation voltage V(2), and the oscillation of the pilot signal CPLT is started at time T(4), whereby the preparation for charging is started. When the preparation for charging is completed and the switch SW(1) is turned on at time T(5), the voltage of the pilot signal CPLT further lowers to the voltage V(3). As a result, the relay 332 inside a connector 310 inside the charging cable 300 is turned on, and the relay switch on the route of charging on the side of the vehicle is also turned on, whereby charging is started.